1. Field of the Invention
The present invention relates to an apparatus for recording an image on a CRT (cathode-ray tube), employed mainly for medical purposes and which is capable of recording a plurality of images on a single sheet of film.
2. Description of the Prior Art
In a conventional variable-magnification CRT image recording, or photographing, apparatus, a mirror is disposed on the optical axis of a CRT so as to orientate the optical path horizontally, and the image displayed on the CRT is recorded on a sheet of film through a lens (see Japanese Utility Model Laid-Open No. 25519/1984). The apparatus enables the record, or photography, of the CRT image at any desired magnification, by moving the CRT and lens appropriately. The movement of each is effected in accordance with values previously stored in a microcomputer for each degree of magnification.
This type of CRT image recording apparatus, however, suffers from the following disadvantages. Since the lens is interposed between the mirror and the film and since the degree of magnification is varied by moving the lens, it is necessary to increase the length of the apparatus, which results in an increase in the area required for the installation of the apparatus.
Further, since there may be variations in the focal lengths of lenses due to dispersions in manufacture, it is necessary, when using the conventional apparatus, to adjust the focus for each degree of magnification selected during photography.
In the medical diagnosis field, one type of apparatus has heretofore been utilized in which a plurality of images displayed on a monitor (CRT) are separately formed on a single sheet of film.
This known type of recording apparatus includes the apparatus which is disclosed in the specification of Japanese Patent Laid-Open No. 60937/1980. In this apparatus, a sheet of film is disposed above a monitor (CRT) whose screen points upward, and a photographic lens is disposed between a film conveyor device and the monitor. The film can be moved by the conveyor device, and the monitor can be moved parallel to the plane of the film. In this way, a plurality of images displayed on the monitor can be separately formed on the surface of a single sheet of film by moving the film and the monitor relative to each other.
This type of recording apparatus, however, suffers from the problem that the film, which is disposed horizontally, may be flexed, or bent, by its own weight, and this may make impossible to obtain good-quality pictures. Support of the film is particularly insufficient in the vicinity of the optical axis, because it is necessary at this position to provide enough space to ensure that the optical path of the exposure light is not obstructed, which results in a large degree of flexure and unreliable conveyance of the film.
When exposure is effected in a state wherein the film is disposed so that its plane is vertical, the film may similarly be flexed between a plurality of rollers constituting the film transporting device, thus adversely affecting the planar characteristics of the film. To overcome this problem, an arrangement is also employed in which each sheet of film is housed in an individual cassette which is positioned in the optical path, and exposure is effected through a window formed in the cassette. However, this arrangement employing cassettes necessitates a troublesome handling operation and a complicated structure.